1. Field of the Invention
The invention is directed to an improved high-pressure pump for a fuel injection system of an internal combustion engine
2. Description of the Prior Art
A high-pressure pump known from DE 199 07 311 A1 has a housing and several pump elements situated in the housing. Each of the pump elements has pump piston that is set into a stroke motion by a drive shaft of the high-pressure pump. The pump piston is guided in a sealed fashion in a cylinder bore of housing part of the high-pressure pump and delimits a pumping chamber in the cylinder bore. The pump piston is supported against the drive shaft by means of a support element in the form of a tappet. A prestressed return spring acts on the pump piston in the direction of the tappet and acts on the tappet in the direction of the drive shaft. A roller is supported in the tappet in rolling fashion and supports the tappet against a cam of the drive shaft. The tappet is guided so that it can slide in a bore contained in another housing part of the high-pressure pump separate from the housing part containing the cylinder bore; the bore and the tappet have a significantly larger diameter than the cylinder bore. A disadvantage of this known high-pressure pump is that the cylinder bore in which the pump piston is guided and the bore in which the tappet is guided are contained in separate housing parts so that assuring an exact alignment of the cylinder bore and the bore for the tappet requires complex centering measures to align the housing parts in relation to each other. In addition, because of its large diameter, the tappet is heavy, which in turn requires a very rigid and therefore heavy return spring in order to prevent the tappet from lifting up from the drive shaft at high speeds, which results in the high-pressure pump being heavy as a whole.